Satya Nadella at a Microsoft Search Summit event in San Francisco in 2010. / David Paul Morris Bloomberg

by Nancy Blair, USA TODAY

by Nancy Blair, USA TODAY

SAN FRANCISCO - Microsoft CEO Satya Nadella on Thursday unveiled Office for iPad, a highly anticipated and long overdue version of its bread-and-butter productivity software for Apple's popular tablet.

The move enforces Microsoft's recognition that it must deliver services to both businesses and consumers wherever they are, especially on mobile devices.

The iPad apps for Microsoft Word, Excel and PowerPoint are free in Apple's App Store. You'll be able to read and present your content that way, but for creating and editing content, you will need an Office 365 subscription.

The launch marks the "beginning of exploration for us," Nadella said in his opening remarks.

Office software lets you create and edit documents, calculate spreadsheets and design presentations and graphics through its Word, Excel and PowerPoint programs. Microsoft moved to a subscription model for Office last year with Office 365 Home Premium, which runs $9.99 a month, or $99.99 a year. A personal version for one computer and one tablet is due this spring for $69.99 a year.

Mobile Office apps have already been available for iPhone and Android smartphones, with a required Office 365 subscription. As of Thursday, you can edit content for free on phones.

Office on iPad is "a beautiful set of applications," said Nadella, adding that the company is "taking great care to make sure that Office on every device shines through."

Nadella, who last month replaced Steve Ballmer as Microsoft CEO, addressed the importance of a "mobile-first, cloud-first world" for the company and how Office for iPad fits in with both its consumer and corporate strategies as more companies encourage employees to bring their own devices to work.

"This, in a sense, is a cloud for everyone on every device," he said.

Last week, Microsoft stock hit its highest level since 2000 on increasing chatter ahead of the announcement. Shares of Microsoft were down 1% to $39.36 in late trading.

Wall Street analysts and others have pointed to mobile as a crucial part of Microsoft's strategy under Nadella.

Individual consumers initially might be disappointed to discover that they can't download the app for just a few dollars, said Gartner analyst Michael Silver. But Silver called Office for iPad "a major addition" that could entice more people to ante up for an Office 365 subscription.

Ahead of the announcement, Forrester analyst J.P. Gownder said Microsoft realizes that the revenue opportunity associated with Office on iPad - which he said is pegged at an estimated $1.4 billion - outweighs any risks to Windows. It's a welcome addition for Apple as well, he noted, since it adds to the utility of the iPad for business use, especially when coupled with an accessory keyboard.

Nadella reiterated his commitment to making Microsoft applications work on devices no matter the operating system, including those from Apple and Google. At the same time, he affirmed the company's commitment to Windows.

"Windows is a massive agenda for us," he said. "There is no trade-off. This is reality for us."

Microsoft will delve more deeply into its mainstay operating system at a developer conference in San Francisco next week.